In-Pixel Amplification Circuitry for Image Sensor Noise Reduction
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Solution Overview
Problem
Conventional image sensors face noise issues during readout operations, requiring large capacitors that occupy significant substrate area, making it challenging to achieve both global shutter capabilities and reduced noise.
Innovation Solution
Incorporating in-pixel amplification circuitry with first and second amplification capacitors, where the capacitance of the second capacitor is significantly larger than the first, allowing for signal amplification and reducing the need for large storage capacitors, thereby minimizing noise and substrate area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If large capacitors are included in imaging pixels to reduce noise during readout, then noise is reduced, but substrate area occupied increases
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks including photodiode, transfer transistor, floating diffusion, source follower transistor, and amplification capacitors. This segmentation allows each component to be optimized independently, enabling noise reduction through strategic capacitor placement while minimizing overall substrate area.
Solution Approach 2:
The patent utilizes vertical substrate layers to accommodate circuit components. The amplification capacitors are positioned in different vertical layers, allowing three-dimensional integration that reduces the horizontal substrate footprint while maintaining sufficient capacitance values for noise reduction.
2Reliability
If in-pixel amplification circuitry is added to reduce noise and enable global shutter, then performance is improved, but device complexity increases
Solution Approach 1:
The amplification function is merged directly into the pixel circuit by integrating amplification capacitors within each pixel. This eliminates the need for separate post-pixel amplification stages, reducing overall system complexity while achieving the desired noise reduction and global shutter functionality.
Solution Approach 2:
The floating diffusion node serves multiple functions: charge storage from the photodiode, signal amplification through the source follower transistor, and coupling to the amplification capacitors. This multi-functionality reduces the need for additional dedicated components, thereby managing circuit complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The in-pixel amplification circuitry effectively reduces noise and enables global shutter operations while minimizing the size of capacitors required, thus optimizing image sensor design for improved performance and compactness.
Implementation Method 1
Each image pixel may include a photodiode for generating charge in response to incident light
Data Source
AI summary
An image sensor may include an imaging pixel, readout circuitry, and amplification circuitry coupled between the imaging pixel and the readout circuitry. Correlated double sampling may be used to sample a reset voltage and a signal voltage from the imaging pixel. The difference between the reset voltage and the signal voltage may reflect the amount of light received by the imaging pixel during an integration time. The amplification circuitry may amplify the difference between the reset voltage and the signal voltage. The amplification circuitry may include a source follower transistor coupled between first and second capacitors, with the second capacitor having a greater capacitance than the first capacitor. The amplification circuitry may be formed only from n-type metal-oxide-semiconductor transistors. The amplification circuitry may consume power dynamically as opposed to consuming static power for minimal power consumption requirements.